Here's a question/bit of speculation...
I wonder if Another String of Hot Hits was originally intended to be the all new follow-up to String of Hits...?
When it was released in July 1980, about four months after SoH had hit Number One, it was an interesting, but mildly disappointing, compilation of old tracks with just one new one, Black is Black (which must have been recorded in 1979). The front cover artwork is incredible, a melting black Fender Strat, and easily as striking and original as the cover art for SoH. This alone makes me think that this album had been planned and in the pipeline for quite a while. Obviously the Shads severed their ties with EMI in early 1980 and so, rather than waste the commissioned artwork, and wanting to get 'Black is Black' out there, maybe the idea of a compilation album arose as a way of cashing in on the success of the previous album to the fullest degree now possible?
Personally I'd have preferred Another String of Hot Hits if it had, say, the full length version of Don't Cry For Me Argentina and the 45" mix of Riders in the Sky - and I think Black is Black, although not as good, should have been released as a single (in the UK) as the follow-up to Riders...
For the cover image alone, this album was worth getting - and, of course, some of us hadn't even bought Shades of Rock at that point, so some of the tunes were new to us! I just have to wonder if the album might have turned out differently, and better, if the Shads had remained with EMI.